Back to regular scheduled programing, "what the heck was Justin up to???
Curious lines in Cold Days after Justin asks Harry to put on a straight jacket.. Harry asks an important question, "Why?" To which Justin answers;
Justin remained calm. "You don't have the knowledge you need to understand boy. Not yet. But you will in time."
Before that on the same page Harry asks Justin what is going on? And Justin answers;
"I'm making plans, Harry," he said in a steady, quiet voice. "I need people I can trust."
Then in the next chapter after the review of what happened after he fled.. Lea says, he was raising you two up to be enforcers.
So from the above I surmise that Justin had real delusions of grandeur, who knows, by that time he may have been infected and Nemesis was controlling him. So if Harry and Elaine were to be enforcers, just what was it they were going to enforce? But one real possibility, if Justin was infected, in the process of enthralling Elaine, she got infected, and when she ran away to the Summer Court, this is how Aurora got infected.